Recent studies indicate a role for the amygdala in the modulation of attentional processes during .associative learning in rats. Lesions of the amygdala central nucleus (CN) present the normal conditioning of orienting responses (ORs) to conditioned stimuli (CSs) paired with food unconditioned stimuli (USs), and interfere with the enhancement of CS associability normally observed when contingencies between the CS and other events are altered. For its primary focus, the proposed research would more fully characterize the behavioral determinants and nature of CN-mediated attentional changes and would investigate the neural circuitry involved in those changes. The experiments in specific aim 1 are based on well-developed behavioral theories of learning and are designed to determine the procedural conditions necessary for activating the CN- mediated incremental CS processing system. The studies in specific aim 2 address the neural circuitry for implementation of amygdala attentional functions, concentrating on a CN-nigral-striatal system for the conditioned OR and CN regulation of basal forebrain corticipetal pathways for enhancement of CS associability. A second focus (specific aim 3) is the exploration of the relation between CN systems underlying attentional regulation and amygdala circuitry responsible for changes in the motivational significance or value of CSs in conditioning (a function more traditionally ascribed to the amygdala). A final set of experiments (specific aim 4) would consider the relation between amygdala circuitry involved in enhancements of attention and hippocampal circuitry implicated in reductions in attention (for example, in latent inhibition). The research would use behavioral techniques, simple and crossed (asymmetrical) lesion procedures with specific neuro- and immunotoxins, and measurements of corticipetal activation using high-affinity choline uptake and c-fos mapping to accomplish these specific aims. The proposed behavioral and neurobiological studies may provide new insights into cognitive functions of the amygdala, as well as relations between cognitive and motivational functions in associative learning.